net: respect hosts file when resolving names for Windows

Fixes #57757.

Change-Id: I896dae8e5905ae98539ab83c9379fd1c9886d44a
Reviewed-on: https://go-review.googlesource.com/c/go/+/467335


Reviewed-by: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Joedian Reid <joedian@golang.org>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>